The National Resource for Accelerator Mass Spectrometry (AMS) was established in 1999 to enable biomedical researchers to accurately quantify very low levels of radioisotopes while exploring fundamental issues in biology. In this renewal, we will expand our present capabilities by developing a fully integrated HPLC AMS to increase our capabilities for metabolic measurements which our collaborators require. We will develop methods to study biochemical pathways and cellular processes down to the level of the single cell. Finally we will develop and validate methods for the application of AMS in human translational research which is a growing area of demand by collaborators and service users. Throughout the tenure of the grant we will continue to provide a resource to the research community that will include service to investigators familiar with AMS, training of investigators in the technology and dissemination of the Resource. Towards these goals, our specific aims are to: 1.) Increased throughput of AMS through direct coupling to separatory instruments. 2.) Increase the value and information content of AMS measurements by combining molecular identities with quantitation of defined isolates for pathway analysis from very small cellular, animal, and human samples. 3.) Provide quantitation of biological systems using multiple isotopic tracers within sampled materials. 4.) Provide high throughput precision quantitation for collaborative and service clients.